Heat oil in a saucepan then soften the onion. Stir in the ginger, garlic, shrimp paste, chilli, lemon zest and juice. Leave for a couple of minutes. Add the curry powder and sugar and keep stirring. When the sugar starts to melt and everything starts to clump together, add the coriander stems, coconut milk and 2 tbsp water then bring to simmer.

Add the fish and prawns to the sauce, then squeeze over half the lime. Pop on the lid and simmer for 20 minutes until hake is cooked and flaking and prawns are pink througout. Season to taste and scatter coriander leaves over to serve with rice.